Fraudulent use of telephone services is known to be a significant problem for telephone companies and their legitimate customers.sup.1. FNT .sup.1 See paper titled IBM Fraud Management System, published on the Internet at http://www.telecom-media.hosting.ibm.com/telemedia/mccawibm.htm
Solutions hitherto proposed involve a "positive" form of identification, the objective of which is to determine if a caller incurring charges is a legitimate user of the line or channel being charged. For instance, a caller's recitation of a prescribed phrase may be compared with a previously recorded sample of the same phrase spoken by a legitimate user of the line or channel to which a respective call is being charged.
The problem with such positive identification techniques is that they tend to be less than completely accurate, and thereby tend to give rise to "false errors" that inconvenience legitimate users. These techniques also tend to inconvenience legitimate callers in other ways (e.g. by requiring recitations of specific phrases, etc.).